Known in feeds for internal combustion engines are air intake pipes with pivoting flaps such as, for example, those taught by Patent Application EP 0 701057. This document teaches a pipe which for each combustion chamber comprises at least two air ducts, at least one of which is selectively closed by a flap that pivots around a shaft that is crosswise to the duct between an at least partially sealing position and a position for opening the duct. In this kind of device, according to the prior art, the metal-flap actuating shaft is mounted in the molded thermoplastic part that constitutes the body of the pipe with journals and rings that require gaskets to ensure the sealing of the shaft at the junction with the plastic parts.
In such a device, the rings can be equipped with flexible or elastically deformable means to limit the radial play of the shaft relative to the body of the thermoplastic device.
Taking into account this possible play, issues of alignment of shafts and of rotation of the shaft relative to the plastic part are dealt with by the additional parts. This has the drawback of requiring the production and installation of additional parts in the thermoplastic part. A first drawback is the increased production cost. In addition, this composition makes it necessary to provide hoods, mounting points, journals and barrels that can be attached to the main part by ultrasonic soldering or by locking. This latter solution does not necessarily ensure that the axis of rotation will be maintained properly relative to the body of the device.
In a variant embodiment of this prior art, the common drive shaft is flexible and comprises duplicate-molded drive segments that are separated by flexible portions. This flexibility facilitates installation by making it possible to compensate for the major misalignments of the cradles and barrels that form the bearings and the range of rotation of the various flaps. The problem of misalignment of the bearings is therefore known, and to date one skilled in the art has not found a satisfactory solution.
Today, to solve the problem of alignment of passages of pins in the successive bearings, several other solutions exist, but each of them has its drawbacks. To obtain the anticipated result, which is to be able to engage a rotating pin freely in the various bearings of a part that follows the same shaft, it is necessary that the passage holes be perfectly aligned if it is desired that this pin be able rotate freely. To do this, it is possible to duplicate-mold a pin that is then withdrawn; this leaves open the possibility of a non-alignment existing after the pin has been withdrawn owing to deformations due to internal tensions. It is also possible to pierce the part over its entire length. Considering the lengths in question, this leads to buckling of the drill, which does not make it possible to ensure perfect alignment. In any case, the machining embrittles the surface that is attacked by the drill. Finally, a last solution that corresponds to that of the European Patent is to study the part to produce it in several parts so that the bearings can be assembled in the molded part.